The present invention relates in general to a device for folding sheet material such as paper, and in particular to a new and useful upset folding machine which has four rollers running parallel to each other in a frame, the rollers being driven by a common electric motor. The rollers are in contact with each other to form a plurality of nips for taking up the sheet material and to form folding lines.
Folders of this type in the prior art have included folding pockets in the vicinity of some of the roller nips. The machine included a feed table and a delivery table.
Folders of this kind have been known for a long time (German patent No. 856,442). In a prior art machine of this construction, the folding pockets are formed by arcuate slots which are provided at uniformly spaced apart locations in sheet metal partitions between two frame walls. The drive motor is accommodated in recesses therebetween. The feed table extends above the delivery table. The frame is not enclosed at all. No housing is provided. In spite of that, undesirably accumulated paper is difficult to remove from this prior art machine. The feed and delivery tables require much space, and so does the assembled machine. In addition, it is necessary with this prior art folder to bring the paper sheets to be individually fed, in advance into an aligned position at a guide rail of the feed table, to avoid oblique folds. The feed table is therefore indispensable for correct folding. Both the bulkiness and the difficulty in remedying disturbances by paper accumulation, etc., make such a machine unsuited for a zig-zag or wrap-type folding of the sometimes sparse daily mail in an office.